Found the solution using the CLI here
GAL Browsing in 6.0 and
GAL Sync Account - Zimbra :: Wiki the admin GUI isn't working logged at bugzilla
code to split and share a GAL for an EDU
Code:
# STAFF
zmgsautil createAccount -a syncac_staff@myorg.edu -n syncac_staff --domain myorg.edu -t ldap -f staff -p 1d
zmprov mds syncac_staff@myorg.edu syncac_staff zimbrasyncacLdapFilter "(&(|(MY_LDAP_FILTER)" zimbrasyncacLdapSearchBase ou=staff,dc=dc=myorg,dc=edu zimbrasyncacLdapURL ldap://myldapserver.edu:389
zmgsautil fullSync -a syncac_staff@myorg.edu -n syncac_staff
zmmailbox -z -m syncac_staff@myorg.edu mfg /staff all r
zmmailbox -z -m a.user@myorg.edu cm -F# /Staff_Address_List syncac_staff@myorg.edu /staff
#STUDENTS
zmgsautil createAccount -a syncac_students@myorg.edu -n syncac_students --domain myorg.edu -t ldap -f students -p 1d
zmprov mds syncac_students@myorg.edu syncac_students zimbrasyncacLdapFilter "(&(|(MY_LDAP_FILTER)" zimbrasyncacLdapSearchBase ou=students,dc=dc=myorg,dc=edu zimbrasyncacLdapURL ldap://myldapserver.edu:389
zmgsautil fullSync -a syncac_students@myorg.edu -n syncac_students
zmmailbox -z -m syncac_students@myorg.edu mfg /students all r
zmmailbox -z -m a.user@myorg.edu cm -F# /Students_Address_List syncac_students@myorg.edu /students